1. Field of the Invention
This invention relates generally to satellite communication systems. In particular, this invention relates to a switching system for distributing one or more satellite signals to multiple set-top boxes (“STB”).
2. Related Art
From the inception of convenient direct broadcast satellite (“DBS”) services such as those offered DBS service providers DirectTV® and DISH Network® in the United States and similar services around the world, there has been a tremendous growth in the number of DBS subscribers. As more subscribers enroll in DBS services, DBS service providers are offering a greater number of services including, but not limited to, addition pay-per view, high definition television (“HDTV”), broadband Internet, satellite radio transmission, and other bandwidth-intensive services. As such, DBS providers require higher throughput to offer these bandwidth-intensive services to their growing number of subscribers.
Typically, the DBS providers are distributing these services among multiple satellites. As a result, this distribution of services or programming among multiple satellites typically requires the installation of one or more satellite antennas (typically known as a “dish” antenna when a reflector antenna such as a parabolic antenna is utilized) in combination with one or more low-noise block downconverters (also known as low-noise blocks “LNBs”).
Until recently, most DBS systems have not allowed multiple STBs to operate in combination with one or more satellite antennas because usually a STB has some intelligence (i.e., it has a processor that runs control software) that controls the LNB based on the channels the STB wants. FIG. 1 shows an example implementation of prior art DBS system 100 in signal communication with a video monitor 102. The DBS system 100 may include a satellite antenna 104, LNB 106 and a STB 108.
The video monitor 102 may be any device capable of receiving the information delivered by the STB 108. Examples of the video monitor 102 may include a television set, a television monitor (without a television receiver), a computer monitor, and/or a video recording device. The STB 108 may be any generally known STB similar to the STBs produced by multiple manufacturers for both DirectTV® and DISH Network®, or other similar types of DBS service provider. Typically the STB 108 is generally known as an Integrated Receiver Decoder (“IRD”), which is a satellite receiver with a built-in decoder for unscrambling subscription channels broadcast by the DBS system provider.
It is appreciated by those skilled in the art that the satellite antenna 104 and LNB 106 are packaged usually together as one unit and the LNB is typically an active device. Examples of the satellite antenna 104 may include an 18-inch reflector antenna (typically know as a “dish antenna”) or any other type of antenna such as a phased array, patch, and/or active or passive antenna. The LNB 106 is generally an amplifier that blocks low-end frequencies and receives the high-end frequencies used in digital satellite transmissions. In many DBS systems utilizing a reflector antenna, the LNB is generally located at the end of the arm projecting from the satellite antenna 104. Typically, a single-output LNB provides one RF output for connecting a coaxial cable to feed the received digital satellite signal to a single STB. A dual-output LNB typically has two RF outputs for distributing satellite signals to two or more STB.
In operation a DBS system, such as DirectTV® and DISH Network®, typically broadcasts each channel from their satellites with either a “left-hand” (known as left-handed circular polarization or “LHCP”) or “right-hand” (known as right-handed circular polarization or “RHCP”) circular polarization. Approximately, half the channels are broadcast with one polarization while the other channels are broadcast with the opposite polarization. Generally, the LNB 106 is capable of only receiving one type of polarization at a time and the STB 108 has an internal memory that contains a table of values (that is typically downloaded from the satellite) that represent the polarization of each channel. The STB 108 then instructs the LNB 106, via signal path 110 (which may be a standard coaxial cable), to switch to the polarization that corresponds to the desired channel of the STB 108. The STB 108 may instruct the LNB 106 to switch between polarizations by placing a variable voltage on the signal path 110.
As a result, the DBS system 100 does not allow multiple STBs to operate on one coaxial cable from the satellite antenna 104 and LNB 106 combination because multiple STBs would not be able to coordinate switching the polarization of the LNB 106. The polarization of a channel selection of one STB would interfere with the polarization of another channel selection on the other STB.
In home environment this is a drawback of DBS systems compared to, as an example, standard non-DBS cable systems. In standard non-DBS cable systems, a cable provider transmits the cable channels (whether analog, digital or combination of both) via one coaxial or fiber optic cable to a home. The residents of the home may then split the coaxial cable with a general-purpose splitter into multiple coaxial cables that are capable of feeding the transmitted cable channels into multiple video monitors via multiple cable receivers (or built-in television receivers within the video monitors). Each cable receiver is then capable of independently and simultaneously selecting different transmitted cable channels.
End-users in a home environment have become accustomed to connecting multiple video monitors and/or cable receivers to a common coaxial system that is the result of simply splitting the input coaxial cable from the cable system. It is appreciated that in a typical modern home almost every room will have a coaxial cable that extends from a wall outlet. All these cables will be connected to either an outside antenna or the cable system via a coaxial splitter.
As a result, end-users in a home environment expect or at least desire a similar convenience from an installed DBS system. Unfortunately, the DBS system 100 is not capable of allowing multiple STBs to connect to the LNB 106 and provide independent simultaneous channel reception by each individual STB.
Present attempts to solve this problem include utilizing multiple LNBs for each STB along with potentially utilizing multi-switches. Generally, DBS systems utilizing a dual LNB type reflector antenna may allow two independent STBs to simultaneously tune into different broadcast channels.
FIG. 2 shows an example implementation of a prior art DBS system 200 in signal communication with a first video monitor 202 and second video monitor 204. The DBS system 200 may include a first satellite antenna 206, second satellite antenna 208, first LNB 210, second LNB 212, first STB 214 and second STB 216. It is appreciated by those skilled in the art that the first satellite antenna 206, second satellite antenna 208, first LNB 210, and second LNB 212 may be incorporated into one dual mode antenna (not shown) such as, for example, a dual LNB antenna for use with DirectTV® and DISH Network®, respectively.
In operation, the first LNB 210 and second LNB 212 are capable of only receiving one type of polarization at a time and the first STB 214 and second STB 216 have internal memories containing tables of values (that are typically downloaded from the satellites) that represent the polarization of each channel. The first STB 214 then instructs the first LNB 210, via signal path 218 (which may be a standard coaxial cable), to switch to the polarization that corresponds to the desired channel of the first STB 214. Similarly, the second STB 216 then instructs the second LNB 212, via signal path 220 (which may again be a standard coaxial cable), to switch to the polarization that corresponds to the desired channel of the second STB 216. Both the first STB 214 and second STB 216 may respectively instruct the first LNB 210 and second LNB 212 to switch between polarizations by respectively placing a variable voltage on the signal paths 218 and 220.
As a result, the DBS system 200 allows the first STB 214 and second STB 216 to operate on two separate coaxial cables 218 and 220 from the first satellite antenna 206 and first LNB 210 and second satellite antenna 208 and second LNB 212 combinations. The first STB 214 and second STB 216 will be capable of independently and simultaneously tuning to separate channels because the first STB 214 and second STB 216 operate on separate independent coaxial cables 222 and 224. Thus, the first STB 214 and second STB 216 will be able to switch the polarization of the first LNB 210 and second LNB 212, respectively, without interfering with each other.
Additional attempts to solve this problem have also included utilizing multiple LNB coupled to multiple STBs via a multi-switch. Generally, DBS systems utilizing a dual LNB type reflector antenna and a multi-switch may allow two or more independent STBs to simultaneously tune into different broadcast channels.
FIG. 3 shows an example implementation of a prior art DBS system 300 in signal communication with multiple video monitors 302, 304 and 306. It is appreciated by those skilled in the art that while only three video monitors are shown, the example implementation is equally applicable to more than three video monitors. The DBS system 300 may include a first satellite antenna 308, second satellite antenna 310, first LNB 312, second LNB 314, multi-switch 316, first STB 318, second STB 320 and third STB 322. It is again appreciated by those skilled in the art that the first satellite antenna 308, second satellite antenna 310, first LNB 312, and second LNB 314 may be incorporated into one dual mode antenna (not shown) such as, for example, a dual LNB antenna for use with DirectTV® and DISH Network®, respectively. Again, it is appreciated by those skilled in the art that while only three STBs are shown, the example implementation is equally applicable to more than three STBs.
In operation, the first LNB 312 and second LNB 314 are capable of only receiving one type of polarization at a time and the first STB 318, second STB 320 and third STB 322 have internal memories containing tables of values (that are typically downloaded from the satellites) that represent the polarization of each channel. The Multi-Switch 316 is coupled to both the first LNB 312, via signal path 324, and second LNB 314, via signal path 326, and controls both by maintaining one LNB (such as, for example, the first LNB 312) in one polarization state (such as, for example, LHCP) and the other LNB (such as, for example, the second LNB 314) in another polarization state (such as, for example, RHCP). The Multi-Switch 316 is also coupled to a plurality of STBs (such as, for example, first STB 318, via signal path 328, second STB 320, via signal path 330, and third STB 322, via signal path 332) and switches an individual coupled STB to the corresponding LNB having the polarization desired by the individual STB.
In this example, when the first STB 318 instructs the Multi-Switch 316, via signal path 328 (which may be a standard coaxial cable), to switch to the polarization that corresponds to the desired channel of the first STB 318, the Multi-Switch 316 couples the first STB 318 to the LNB (either the first LNB 312 or second LNB 314) that is set to the corresponding polarization. Similarly, when the second STB 320 instructs the Multi-Switch 316, via signal path 330 (which again may be a standard coaxial cable), to switch to the polarization that corresponds to the desired channel of the second STB 320, the Multi-Switch 316 couples the second STB 320 to the LNB (either the first LNB 312 or second LNB 314) that is set to the corresponding polarization. Still similarly, when the third STB 322 instructs the Multi-Switch 316, via signal path 332 (which again may be a standard coaxial cable), to switch to the polarization that corresponds to the desired channel of the third STB 322, the Multi-Switch 316 couples the third STB 322 to the LNB (either the first LNB 312 or second LNB 314) that is set to the corresponding polarization.
Again, the first STB 318, second STB 320 and third STB 322 may respectively instruct the Multi-Switch 316 to switch between LRCP and LHCP polarizations by respectively placing a variable voltage on the signal paths 328, 330 and 332.
As a result, the DBS system 300 allows a plurality of STBs to operate on a plurality of separate coaxial cables from the first satellite antenna 308 and first LNB 312 and second satellite antenna 310 and second LNB 314 combinations via the Multi-Switch 316. The plurality of STBs will be capable of independently and simultaneously tuning to separate channels because the plurality of STBs operates on a plurality of separate independent coaxial cables. Thus, the plurality of STBs will be able to switch the polarization of the first LNB 312 and second LNB 314, via the Multi-Switch 316, without interfering with each other.
Unfortunately, the approaches described in FIGS. 1, 2, and 3 are multi-cable approaches that are high cost and cumbersome to arrange in the typical home environment because they include the increased cost of equipment such as multiple cables, multi-switch devices, combiners and splitters and the cost of labor in professionally installing the equipment. Once the equipment has been installed it is pseudo-permanent in nature because it is difficult to rearrange the equipment in the future. These approaches are still much more complicated than adding additional cable ready tuners in a home installed cable television system.
Therefore, there is a need for a system and method that provides a low cost solution for distributing DBS system signals on a signal cable from the DBS antenna to the home environment.
An example of a pervious attempt to solve this problem is shown in FIG. 4. The DBS system 400 is shown in signal communication with a first video monitor 402 and second video monitor 404. The DBS system may include a first STB 406, second STB 408, first satellite antenna 410, second satellite antenna 412, first LNB 414, second LNB 416, Multi-Switch 418, first mixer 420, second mixer 422, frequency reference 424, combiner 426 and splitter 428.
In operation, the DBS system 400 receives the DBS satellite signals via the combination of first satellite antenna 410 and first LNB 414, second antenna 412 and second LNB 416, and the Multi-Switch 418; however, it is appreciated that additional antennas and LNBs may also be utilized. The DBS system 400 then band translates the received satellite signals, via signal paths 430 and 432, with the first mixer 420 and second mixer 422 creating a low-band satellite signal 434 and high-band satellite signal 436. The low-band satellite signal 434 and high-band signal 436 are then combined, via combiner 426, on to one signal path 438 (typically a coaxial cable) that is later split by splitter 428. The splitter 428 then passes the combined signals transmitted on signal path 438 to both the first STB 406 and second STB 408 via signal paths 440 and 442, respectively. Both the first STB 406 and second STB 408 will need to be able to downconvert the received signals to frequency plan that allows both STBs to demodulate and decode the received signals so that the first video monitor 402 and second video monitor 404 are able to display the received channels. As a result, the DBS system 400 allows two STBs to operate independently on a single coaxial cable from the first satellite antenna 410 and first LNB 414 and second satellite antenna 412 and second LNB 416 combinations via the Multi-Switch 418.
FIG. 5 shows a graphical representation 500 of amplitude 502 versus frequency 504 in megahertz (“MHz”) of an example frequency characteristic for both the low-band satellite signal 506 and high-band satellite signal 508. In this example, the low-band satellite signal 506 may occupy the 950 to 1,450 MHz frequency range, while the high-band satellite signal 508 may occupy the 1,650 to 2,150 MHz frequency range with a 200 MHz guard-band 510.
Unfortunately, a drawback to this approach is that it would only operate with two STB because only two frequency bands are supported. The DBS system 400 only translates the high frequency band to a low-band and the low frequency band to a high-band. As a result, one STB (such as the first STB 406) is only capable of receiving a high-band signal and the other STB (such as the second STB 408) is only capable of receiving a low-band signal. Additionally, filter devices (not shown) may be needed at both the first STB 406 and second STB 408 to filter out the undesired bands. Moreover, the DBS system 400 has very low selectivity and that does not allow fine-tuning of the received channels.
Therefore, there is a need for a system and method that provides a low cost solution for distributing DBS system signals on a signal cable from the DBS antenna to the home environment that is capable of supporting more than two STBs and has superior selectivity.